Various methods have been disclosed to make printing inks suitable for printing either hydrophilic (hydrogel) contact lenses or the molds that are then used to make hydrogel contact lenses. For example, U.S. Pat. No. 4,668,240 to Loshaek discloses colored inks comprising at least one pigment, a binder polymer having the same functional groups (such as, —COOH, —OH, or —NH—R, wherein R is hydrogen or C1 to C8 alkyl), and an additional compound having at least two groups per molecule selected from at least one of —NCO and epoxy. Loshaek discloses that his inks are suitable for hydrophilic contact lenses produced with a lens polymer that contain one or more of the functional groups —COOH, —OH, or —NH—R, wherein R is hydrogen or C1 to C8 alkyl. The lens and binding polymers are then bound to each other by the reaction of the groups —COOH, —OH, or —NH—R in the lens or the binder polymer and binding polymers with the groups —NCO or epoxy in the binder polymer or the lens. Narducy, et al. discloses in U.S. Pat. No. 4,857,072 that the Loshaek inks are also suitable for hydrophilic contact lenses made of a lens polymer that is substantially devoid of the functional groups —COOH, —OH, or —NH—R, wherein R is hydrogen or C1 to C8 alkyl.
U.S. Pat. No. 5,272,010 to Quinn discloses an ink comprising at least one pigment, binder polymer having the same functional groups (such as, —COOH, —OH, or —NH—R, wherein R is hydrogen or C1 to C8 alkyl), and an adhesion promoter having at least two functional groups per molecule of the formula —CH2 —O—R1 wherein R1 is hydrogen or C1 to C16 alkyl, and said —CH2—O—R1 groups are attached to a carbon atom that is part of an aromatic ring, or attached to a nitrogen or oxygen atom. The Quinn ink is suitable for hydrophilic contact lenses similar to that of U.S. Pat. Nos. 4,668,240 and 4,857,072.
U.S. patent application publication No. 2003/0054109 to Quinn, et al. discloses an ink comprising at least one colorant, and a binder polymer having latent crosslinkable pendent groups (e.g., epoxy, hydroxy, alkenyl, isocyanate, peroxy, perester, anhydride, silane, and combinations thereof). Such inks are substantially free of a separate adhesion promoter species such as hexamethylene diisocyanate or hexamethoxymethylmelamine and are for hydrophilic contact lenses.
However, inks described in the prior art are for non-silicone hydrogel lenses and would be undesirable for use with silicone hydrogels. In recent years, silicone hydrogel contact lenses, for example, Focus NIGHT & DAY™ (CIBA VISION), have become more and more popular because of corneal health benefits provided by their high oxygen permeability and comfort. Inks described in the prior art may not be compatible with silicone hydrogel lenses, since they are designed for conventional (non-silicone) hydrogels and not for silicone hydrogel lenses. They may have adverse effects to the properties (e.g., oxygen permeability, ion permeability, etc.) of silicone-hydrogel lenses and may even affect lens parameters such as base curve and diameter because they are not compatible with the lens polymer.
Therefore, there are needs for a method for making colored silicone hydrogel contact lenses, and for inks suitable for printing a high-quality color image on a silicone hydrogel contact lens.